Ink jet printer

Abstract

An ink jet printer includes pumped-forced circulation of ink through the printer head and a nozzle cap which together eliminate gas from the ink supply and overcome ink stagnation which adversely affect printing quality. Ink from a tank circulates through the printer head and returns to the tank while the nozzles are capped. A brief flow of ink from the nozzles completes a purging of the head prior to printing.

What is claimed is: 
     
       1. An ink jet printer comprising: a printer head including a substrate, a vibration plate, at least one pressure chamber and nozzle formed by providing a gap between said substrate and said vibration plate, each said pressure chamber being connected to one of said ink nozzles;   ink tank means for containing ink for printing;   a reservoir having an inlet and an outlet each said pressure chamber being connected by a channel to said reservoir for receiving ink from said reservoir, said ink reservoir having a low hydraulic resistance to fluid flow from said inlet to said outlet relative to the hydraulic flow resistance through said pressure chambers, channels and nozzles;   first tube means for connecting said ink tank means to said printer head inlet;   second tube means for connecting said printer head outlet to said ink tank means, ink flowing from said ink tank means passing through said ink reservoir from said inlet to said outlet to expel gas bubbles and return to said ink tank means without loss of ink.   
     
     
       2. An ink jet printer as claimed in claim 1, and further comprising means for impelling ink from said tank means through said printer head, whereby flow circulation and bubble purging is accelerated. 
     
     
       3. An ink jet printer as claimed in claim 2, and further comprising valve means for selectively opening and closing one of said first and second tube means. 
     
     
       4. An ink jet printer as claimed in claim 3, wherein said ink tank means is a tank, said first and second tube means being connected to said tank, said means for impelling being a pump. 
     
     
       5. An ink jet printer as claimed in claim 4, and further comprising selectively removeable cap means for selectively covering the outlets of said at least one nozzle. 
     
     
       6. An ink jet printer as claimed in claim 5, wherein said cap means is adapted for wiping said at least one nozzle as said at least one nozzle is uncovered. 
     
     
       7. An ink jet printer as claimed in claim 4, wherein said valve means is in said second tube means. 
     
     
       8. An ink jet printer as claimed in claim 7, and further comprising an air vent in said tank. 
     
     
       9. An ink jet printer as claimed in claim 3, wherein said ink tank means is at least a first and second tank, said first tube means being connected to said first tank and said second tube means being connected to said second tank. 
     
     
       10. An ink jet printer as claimed in claim 9, and further comprising means for impelling ink from said second tank through said second tube means and said printer head, whereby two directional flow through said head is possible. 
     
     
       11. An ink jet printer as claimed in claim 10, wherein said valve means is in said first tube means. 
     
     
       12. An ink jet printer as claimed in claim 1, and further comprising an end plate, and wherein said ink reservoir is formed by providing a space enclosed by said substrate, said vibration plate and said end plate. 
     
     
       13. An ink jet printer as claimed in claim 1, wherein said ink reservoir is formed by a gap between said substrate and vibration plate produced simultaneously with forming said pressure chambers. 
     
     
       14. A method for expelling gas bubbles from a printer head, said head including an inlet port, an outlet port, an ink reservoir and at least one discharge nozzle for ink flow, said inlet and outlet port being connected to said reservoir, said nozzle being connected to a pressure chamber, said pressure chamber being connected to said reservoir, comprising the steps of: (a) blocking said at least one discharge nozzle by cap means;   (b) forcing ink under pressure through said head from said inlet port to said outlet port;   (c) releasing said blocking provided by said cap means until ink flows from said at least one nozzle.   
     
     
       15. A method as claimed in claim 14, and further comprising the step of (d) blocking said outlet port while said ink is forced and said at least one nozzle is unblocked. 
     
     
       16. A method as claimed in claim 14 or 15, and further comprising the step of collecting the ink discharge from said outlet port and returning said ink to a tank supplying said inlet port. 
     
     
       17. A method as claimed in claim 14, and further comprising the step of (d) wiping said at least one nozzle by said cap means while ink is flowing from said at least one nozzle. 
     
     
       18. An ink jet printer comprising: a printer head including at least one pressure chamber, at least one nozzle communicating with said pressure chamber;   ink supply means for providing ink in said at least one pressure chamber;   cap means for capping and cleaning said nozzle, said cap means including a flat portion and a curved portion and being mounted for rotation between an open position and a closed position, said flat portion being spaced from the discharge opening of said nozzle when said cap means is in said open position, said curved portion pressing against said discharge opening of said nozzle and stopping said nozzle when said cap means is in said closed position, said curved portion wiping said discharge opening when rotating between at least one of said open and closed position and said closed and open position, whereby said nozzle may be sealed when printing is stopped, exposed to permit printing, and cleaned in the sealing and exposing process.